Phylogenetic Diversity of Nitrogenase Reductase Genes and Possible Nitrogen-Fixing Bacteria in Thermophilic Chemosynthetic Microbial Communities in Nakabusa Hot Springs.

摘要: Chemosynthetic microbial communities develop and form dense cell aggregates in slightly alkaline sulfidic hot springs the temperature range of 70-86°C at Nakabusa, Japan. Nitrogenase activity has recently been detected collected. To identify possible members capable nitrogen fixation, we examined diversities 16S rRNA nitrogenase reductase (NifH) gene sequences four types chemosynthetic with visually different colors thicknesses. The results a analysis indicated that all had similar bacterial constituents; phylum Aquificae was dominant member, followed abundance by Thermodesulfobacteria, Firmicutes, Thermotogae. Most NifH were related to reported hydrothermal vents terrestrial springs. phylogenetic revealed diversity this among collected, distributed within 7 groups. affiliated (Hydrogenobacter/Thermocrinis) Firmicutes (Caldicellulosiruptor) abundant. At least two energy metabolic pathways appeared be fixation analyzed; aerobic sulfur/hydrogen-oxidizing bacteria fermentative Firmicutes. characteristics these phyla differed from those previously inferred assays on communities, which associated hydrogen-dependent autotrophic sulfate reduction. These may correspond observed are distantly known species Thermodesulfovibrio sp. (Nitrospirae) present study. activities nitrogen-fixing organisms depend redox states as well availability electron donors, acceptors, carbon sources.